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Hi,
I'm an aerospace student at Southampton University and am currently writing my dissertation on:
'Electric propulsion for a manned mission to Mars'
I'm trying to find any information on Delta V's for low thrust Mars trajectories. I know they vary depending on the type of thruster any most projects use computer programs to calculate low thrust trajectories.
But i could really do with values for the Delta V and corresponding specific impulse and thrust of the thruster.
Thanks very much
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Hi,
I'm an aerospace student at Southampton University and am currently writing my dissertation on:
'Electric propulsion for a manned mission to Mars'I'm trying to find any information on Delta V's for low thrust Mars trajectories. I know they vary depending on the type of thruster any most projects use computer programs to calculate low thrust trajectories.
But i could really do with values for the Delta V and corresponding specific impulse and thrust of the thruster.
Thanks very much
Hi mjp!
One of the main problems with human missions to Mars is exposure to radiation, using a low thrust trajectory would worsen this problem.
Approximate values:
delta-v
LEO to Mars surface: 4.8 km/sec
LEO to Phobos: 5.6 kms/sec
Ion thruster: Isp ~ 3000 secs, Thrust ~ 0.1 N
A good place to start reading would be the WP Ion Engine article, also try the search function here in the forum.
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Hi cIclops
Thank you very much for the data I'm sure its going to prove very useful, if anyone has any more low thrust trajectory data please leave me a message or email me.
I'm trying to build up enough data to allow me to graph some results and get an idea of the delta V required for the mission i am planning, but its difficult as nearly all reference missions use software programs to calculate their trajectory for them and thus don't include the delta V's in their report.
Any help is much appreciated
Many Thanks
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Thats partly because the exact Delta-V you need to get there varies on what year it is, what orbit you are in around Earth, and your acceleration (needed to counter gravitational losses). I think the numbers cited above are likely a minimum value at the "best" launch window for high acceleration vehicles. I would consider adding an extra, say, 5% on top for margin if you want to use a low-thrust engine.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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If you will plan whole trajectory and mission, then you could split travel into two parts.
a) From LEO to high earth orbit (2:1 moon synchronous orbit, L1, L2, HEEO,..). This part of the mission would be time insensitive (it could wait in final orbit) and could be made unmanned (The crew could arrive from Earth in few days on a Orion/Soyuz type of ship), since it will travel though Van Allen belt radiation. This part would need 3 - 3,8 km/s delta-v, which is 2/3 of the needed delta-v to get to Mars from LEO.
b) From high earth orbit (near Earth Escape velocity) to Mars. To get from there to Mars transfer orbit you would need around 1 km/s delta-v. This part could even use moon fly-bys to reduce needed delta-v. Capture to Mars orbit or Mars surface could be made with aerobraking or with low thrust/high isp engine. Orbits around L1/L2 would allow greater flexibility while the elliptical earth orbits would need smaller delta-v to reach.
This might help: http://en.wikipedia.org/wiki/Delta-v_budget
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Hi ejp,
Calculating a low thrust trajectory is more of an art than a science at the moment and requires mathematics typically not taught at the UG level. There are a couple tools by NASA (SEPTOP) used as JPL for validating low-thrust trajectories. It is very much an 'end first' operation and the more fleshed out your mission the better. An associate did some calculations a few years back, I'll see if I can look them up for you (just moved, please be patient).
In the meantime, the following website should be useful: http://trajectory.grc.nasa.gov/tools/
edit: Keep in mind that low-thrust trajectory is of little value for a manned mission, though it may be useful for cargo and larger unmanned missions. You may want to check out VASIMR and contact Dr. Franklin Chang-Diaz. He is a very nice guy and understand many of the practical challenges to such a system.
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Hi ftlwright,
Thanks for your reply i'll have a look at that website. I agree with you i don't think its the most suitable form of propulsion for a manned mission.
However the title of the project forces me to focus in that area so its a case of making the best of a bad situation.
Cheers
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Hi ejp,
Calculating a low thrust trajectory is more of an art than a science at the moment and requires mathematics typically not taught at the UG level. There are a couple tools by NASA (SEPTOP) used as JPL for validating low-thrust trajectories. It is very much an 'end first' operation and the more fleshed out your mission the better. An associate did some calculations a few years back, I'll see if I can look them up for you (just moved, please be patient).
In the meantime, the following website should be useful: http://trajectory.grc.nasa.gov/tools/
edit: Keep in mind that low-thrust trajectory is of little value for a manned mission, though it may be useful for cargo and larger unmanned missions. You may want to check out VASIMR and contact Dr. Franklin Chang-Diaz. He is a very nice guy and understand many of the practical challenges to such a system.
But keep in mind that Dr Diaz may have himself a nice engine some day, but he doesn't have a good way to power it. VASIMR is a pipe dream without a revolutionary next-next-generation nuclear power plant probably.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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